From the foregoing some idea of the gigantic nature of the task will be obtained, and we can pass on to a more detailed account of the actual work. Minesweeping may be divided into eight well-defined sections, as follows:-- (1) _Fleet Sweeping._--Keeping clear the sea routes of the battle fleet. (2) _Exploratory Sweeping._--Searching the sea for isolated groups or fields. (3) _Routine Sweeping._--The daily or weekly sweeping of areas, channels and coastal trade routes, largely used by shipping. (4) _Clearing Large Mine-fields._--Big concentrations of ships to rapidly clear important routes temporarily blocked by large mine-fields. (5) _Special Shallow-Water Sweeping._--Such as that carried out off the Belgian coast by specially constructed shallow-draught ships, frequently with single-ship sweeps. (6) _Convoy Sweeping._--Precautionary sweeping in front of incoming and outgoing convoys. This was regularly done even if the fair-way was covered by routine sweeping. (7) _Harbour Sweeping._--Precautionary sweeping usually carried out by small craft at big naval bases such as Portsmouth (Spithead) and Rosyth (Firth of Forth) inside the submerged defences. (8) _Searching at Low Tide._--This was done by shallow-draught vessels of the M.L. type in order to locate badly laid mines which might project above the surface at low water. Several hundred were discovered in this way. In order to carry out these duties efficiently the heterogeneous fleet of minesweepers was divided into small fleets stationed at the numerous anti-submarine bases, and these were again subdivided into units of ships especially adapted for the different classes of work. Each _pair_ of vessels had to be more or less alike in size, draught, speed and manoeuvring ability to enable them to work efficiently in dual harness. Consequently there were complete units of vessels specially constructed for dealing rapidly with discovered mine-fields and for use with the battle fleets. Shallow-draught vessels of the motor launch type for work in the shallow water off the Belgian coast. Converted pleasure steamers of the usual Thames, Mersey and Clyde type for convoy sweeping. Motor launches for clearing fair-ways and for searching at low water. Flotillas of trawlers and drifters for the hard and monotonous routine sweeping on the important coastal trade routes. They comprised in all several thousand ships engaged solely on this work.